Analysis of notions of diagnosis

Various formal theories have been proposed in the literature to capture the notions of diagnosis underlying diagnostic programs. Examples of such notions are: heuristic classification, which is used in systems incorporating empirical knowledge, and model-based diagnosis, which is used in diagnostic systems based on detailed domain models. Typically, such domain models include knowledge of causal, structural, and functional interactions among modelled objects. In this paper, a new set-theoretical framework for the analysis of diagnosis is presented. Basically, the framework distinguishes between 'evidence functions', which characterize the net impact of knowledge bases for purposes of diagnosis, and 'notions of diagnosis', which define how evidence functions are to be used to map findings observed for a problem case to diagnostic solutions. This set-theoretical framework offers a simple, yet powerful tool for comparing existing notions of diagnosis, as well as for proposing new notions of diagnosis. A theory of flexible notions of diagnosis, called refinement diagnosis, is proposed and defined in terms of this framework. Relationships with notions of diagnosis known from the literature are investigated.